The invention relates to multimedia presentations in which graphics objects are presented interactively over a video background.
The invention relates to an apparatus for playing back a record carrier on which are recorded at least a first stream of data representing a video item, a second stream of data representing a graphics item, and a control program for controlling interactive playback of said items, said apparatus comprising,
means for selecting a stream of data to be read from the record carrier, which means are controlled by the control program,
reading means for reading the control program and the selected stream from the record carrier,
video generating means for generating a pixel based representation of the video item in the first stream,
graphics generating means for generating a pixel based representation of the graphics item in the second stream, input means for receiving user input,
which apparatus is adapted for executing a first program portion of the control program which comprises at least primary data relating to shape properties of a graphics object, for executing a test for compliance of user input with a condition specified in the control program and for executing a second program portion of the control program for giving visual feedback in response to the user input,
The invention further relates to a method for playing back a record carrier, said method comprising the following steps,
reading a control program having a first and second program portion from the record carrier,
executing the first program portion comprising primary data relating to shape properties of a graphics object,
requesting user input,
performing a test comprised in said program for compliance of said user input with a condition,
upon compliance of the user input with said condition executing the second program portion for giving visual feedback to the user input,
selecting a stream of data representing a video item and/or a graphics item, the selection being dependent on the user input,
reading said stream from the record carrier and generating a pixel based representation from the item in said stream.
The invention further relates to a record carrier on which is recorded at least
a first stream of data representing a video item,
a second stream of data representing a graphics item,
a control program for controlling interactive playback of said items, which program has a first program portion which comprises primary data relating to shape properties of a graphics object and a second program portion which is to be executed after the first program portion in case of compliance of user input with a predetermined condition specified in the program, which second program portion specifies a visual feedback in response to the user input.
The invention also relates to a method of manufacturing a record carrier according to which method
a first stream of data representing a video item is stored at the record carrier,
a second stream of data representing a graphics item is stored at the record carrier,
a control program for controlling interactive playback of said items is stored at the record carrier, which program has a first program portion which comprises primary data, relating to shape properties of a graphics object and a second program portion which is to be executed after the first program portion in case of compliance of user input with a predetermined condition specified in the program, which second program portion specifies a visual feedback in response to the user input, characterised in that the second program portion comprises secondary data, relating to at least an additional visual property of the graphics object.
The SVCD standard as layed down in the working draft SC100B/NP177/PTD-003 specifies an apparatus for playback of play items, a play item being an audio, and/or a video and/or a graphics item. If so desired a graphics item can be reproduced synchronously with a video item, e.g. in the form of subtitling accompanying a video item. A pixel based representation is to be interpreted as a representation in the form of a two-dimensional array of picture elements. According to the SVCD standard the apparatus is to comprise means for controlling interactive playback of the items at the record carrier by means of a play back control program. This program comprises structures denoted as xe2x80x9cplay listxe2x80x9d and xe2x80x9cselection listxe2x80x9d. The former structure specifies a sequence of play items to be played sequentially. The latter structure enables a user to choose which play items are to be reproduced and in which order. The selection list contains amongst others a reference to a play item. The latter is for example a graphics item which comprises a graphics object representing a menu having different menu parts which correspond to play items at the record carrier which are available to the user. The menu parts for example are in the form of a short description of the corresponding play item or a logo representing the available play item. The shape properties of a graphics object are defined as properties necessary to reconstruct the shape of the graphics object in the pixel based representation. In the SVCD standard the shape properties are defined in the structure xe2x80x9cdisplay dataxe2x80x9d in the form of runlength encoded data. The reference in the selection list is primary data relating to the shape properties in that it refers to the graphics item comprising the display data. The selection list in addition contains references to play items from which the user can make a choice (available play items) and assigns a rectangular region to each of the available play items. By pointing at a rectangular region, the user can focus on an available play item. That available play item can subsequently be activated by the user, for example by pushing a button. By focussing on or activating an available play item the menu part within the corresponding rectangular region is highlighted as a visual feedback upon the user input. Highlighting of the rectangular region is realised by means of a color lookup table. In the rectangular region corresponding to the play item which is focussed upon or activated the color lookup table is loaded with color values differing from those outside the rectangular region. This has the disadvantage that a menu part can only be highlighted individually if that menu part has a rectangular region which does not contain another menu part. This restricts the feedback capabilities of the known apparatus.
The above references are hereby incorporated herein in whole by reference.
It is a purpose of the invention to provide means which enable an improved feedback upon user input.
According to this purpose the apparatus is characterized in that, the second program portion of the control program comprises secondary data which relates to an additional visual property of the graphics object, the apparatus being adapted for generating the visual feedback by reproducing a pixel based representation of the graphics object on the basis of the primary data and the secondary data.
According to this purpose the method for playing back is characterised in that the second program portion comprises secondary data relating to at least one additional visual property of the graphics object and in that the visual feedback is a representation of the graphics object on the basis of the primary and the secondary data.
According to this purpose the record carrier of the invention is characterised in that the second program portion comprises secondary data, relating to at least an additional visual property of the graphics object.
According to this purpose the method for manufacturing a record carrier is characterised in that the second program portion comprises secondary data relating to at least an additional visual property of the graphics object. The measures of the invention enable an improved response to user input.
According to these measures execution of the second program portion of the control program has the effect that an additional visual property to which the secondary data is related is assigned to the graphics object, the shape properties of which were assigned in the first program portion.
An attractive embodiment is characterised in that the graphics object comprises two or more parts, for example menu parts, having mutually different color codes and in that the secondary data relates to at least one color vale which is to be assigned to a color code. By assigning a color value to a part of a graphics object, instead of assigning the color to a region it is possible to individually highlight that part even in the case that no region exists which exclusively contains said part.
In practice some tens of available play items may be available at the record carrier. In an attractive embodiment the color code is represented by at least 6 bits. This enables the apparatus to separately highlight an object part corresponding to each of the available play items.
Another additional visual property is for example visibility. This property may be used to selectively display one of a set of object parts. The set of object parts is for example a set of arrows which each point to a further set of object parts which each symbolize an available play item. Again another additional visual property of a graphics object which can be assigned is for example the location at which it is to be displayed. A further additional visual property of a graphics object is its orientation. The graphics object in the latter two cases is for example an arrow which is overlayed on a video image. Visual feedback is given by having the arrow point to an object within the video image.
Preferably the primary data is related to the shape properties in that the primary data is a reference to a data structure comprising shape data representing the shape properties. This has the advantage that the control program can be relatively small, so that it can be easily resided in an internal memory of the apparatus for playing back. Otherwise the control program may comprise the shape data. In both cases the feedback to user input is not retarded by loading the shape data, because loading has already taken place before the user input is requested.
Preferably the datastructure comprises further data, the secondary data being related to the additional visual property in that the secondary data comprises modification data which includes a reference indicating the location of said further data within the datastructure, the modification data and the further data representing the additional visual property. This has the advantage that the modification data and therewith the control program can be compact. Said datastructure comprising the shape data and the further data can already be loaded in a memory of the apparatus before the user input is requested so that the process of loading the further data does not retard the visual feedback.
The control program may comprise a plurality of first and second program portions for example to present a nested structure of menus to the user. As the datastructures are not included in the program, but referred to by the primary data only that datastructure which is relevant to the current request for user input need be present in the memory, so that the amount of memory required is limited.
It is particularly advantageous if the further data comprises one or more color values. A relatively large set of color values may be required to enable visual feedback in practical cases. By this measure it is achieved that the set of color values need not be incorporated in the control program. The modification data included in the program is for example in the form of a command comprising the reference which instructs a play back apparatus to load one or more color values into a color lookup table starting from a location in memory indicated by the reference.
In an advantageous embodiment of the record carrier the data comprised in the second stream and the data related to the graphics object are in a form which can be processed by common graphics generating means. This has the advantage that an apparatus can be used in which the graphics generating means not only generate a pixel based representation of the graphics item in the second stream, but also generate the pixel based representation of the graphics object.
The apparatus preferably is adapted for executing timing commands in the control program. This has the advantage that the visual feedback can be given in a dynamic form. A dynamic visual feedback provides an efficient way to alert the user.
An attractive embodiment of the apparatus is characterised in that the graphics generating means comprise graphics decoding means for generating an intermediate pixel based representation, storage means for storing the intermediary pixel based representation and graphics modification means for generating a pixel based representation from the intermediary pixel based representation on the basis of the modification data. This embodiment makes it possible to store the intermediary pixel based representation of the graphics object before user input is requested and to compute a pixel based representation from that intermediary pixel based representation after the user input is received. Therewith, the response time between user input and visual feedback is further shortened. Several possibilities exist for representing the shape of the graphics objects. The shape date may for example be in the form of a set of codes which indicate for each of a set of pixels whether it is a background pixel or whether it is an object pixel. In case that the object contains more than one part the code may indicate to which part the pixel belongs. The shape data may for otherwise be in a compressed form, for example in the form of a contour based coding, for example a coding of parts in the object in the form of a list of lines bounding the object. In another embodiment the object parts are encoded in the form of a block code, wherein the shape of the object part is encoded in the form of a plurality of blocks of decreasing size. In a preferred embodiment the shape data is compressed in the form of a run length code. This has the advantage that the intermediary pixel based representation can be generated with relatively simple hardware while a considerable data reduction is achieved.
It is noted that the first and the second streams are not necessarily separate from each other. They may be multiplexed in a common stream. Multiplexing the video and the graphics stream is very useful if a video item and a graphics item (for example subtitling) are to be reproduced synchronously with each other.
In an embodiment the apparatus of the invention has digital outputs for providing a first, a second and a third image signal which respectively represent the pixel based representation of the video item, the pixel based representation of the graphics item and the pixel based representation of the graphics object to a display device. A third image signal is superfluous in an embodiment of the apparatus wherein the graphics generating means both generate the pixel based representation of the graphics item and the pixel based representation of the graphics object.
The display device referred to in the previous paragraph may on its turn have combination means for generating a resulting pixel based representation from said image signals, and a video generator for generating a video signal from said resulting pixel based representation. Otherwise the display device may have a video generator for generating an elementary video signal from each of the incoming image signals and combination means for generating a resulting video signal from the elementary video signals. The combination means may for example superpose the image/video signals, or temporarily select one of the image/video signals or locally select one of the image/video signals. The modification data of a graphics object may contain data relating to a setting of the combination means.
Such a display device may be integrated with the apparatus of the invention.